Tube forming roll



Jan. 22, 1935. R. c. F. K-URTZE 1,989,059

TUBE FORMING ROLL Original Filed Sept. 1, 1931 2 Sheets-Shae 1 Mal a CJan. 22, 1935. R. or. KURTZE 1,939,059

TUBE FORMING ROLL Original Filed Sept. 1. 1931 2 Sheets-Sheet 2 INVENTORPatented Jan. 22, 1935 UNITED STATES PATENT OFFICE Morgan, administratorof said Kurtze, deceased, assignor to Republic Steel Corporation,Youngstown, Ohio, a corporation of New Jersey Application September 1,1931, Serial No. 580,841 Renewed June 12, 1934 'IClaims.

This invention relates to improvements in the structure of roll passesfor forming a metal tube by bending a flat strip of metal longitudinallyand progressively to cylindrical shape.

A tube is formed by moving a flat strip of metal longitudinally througha series of shaping passes for bending the edges of the strip togetherto formthe seam of a continuous cylinder. These passes have comprisedrolls with faces opposed to each other and shaped to appropriate contourfor bending the strip. The passes are adjusted to separate the opposedshaping faces commensurately with the thickness and position of themetal blank, and the rolls are driven to advance the strip by frictionalcontact.

-In operation, one difficulty is that strips tend to be twisted out ofalignment in being propelled through the passes, so that the seam isskewed from a straight line. This turning of the walls of the blankconsumes considerable energy and leaves the metal in undesirableconditions of strain that weaken the tube both mechanically and inresistance to corrosion. Twisting of the blank also makes it diilicultsubsequently to feed the tube properly through a welding machine.

With tubes of large diameter or of heavy wall, increasing numbers offactors contribute to faulty alignment of the seam and of the sidewalls. Irregularities in the thickness of the blank become moreimportant, greater pressures are required to bend the greater mass ofmetal, and the faces of the rolls become distorted more easily. Ingeneral, the maintenance of proper alignment in a metal blank duringbending becomes a more pronounced problem with increase in wallthickness or in diameter of the tube being formed.

It is an object of this invention to improve the structure of rollpasses so as to decrease skewing of an elongate blank during bending totubular form. A further object is to provide roll passes that containshaping elements appropriate for bending even heavy wall or wide stripsto continuous cylindrical form, and that retain the shaping elements insuitable alignment despite con-- siderable usage.

According to this invention, these objects are accomplished in part byproviding roll passes with arcuate forming rolls having the middleportion of the concave bending faces recessed out of the general contourof the pass, the passes containing an opposed convex roll to pressagainst only the edge portions of the concave shaping face. One or moreof the rolls in a pass preferably is mounted yieldably, so that duringoperation its ends may adjust themselves to any unsymmetrical variationsin thickness of a strip. A further element of this invention thatcontributes to maintenance of alignment is the provision of pairs ofinner shaping rollers supported to press against each other and to pressagainst the inner side walls in cooperation with corresponding exteriorforming rolls. Preferably these inner rollers are supported on spindlesthat extend through the seam space at the more nearly cylindricalportions of the blank.

Figs. 1 to 9 respectively are elevations of pinch rolls and of eightsubsequent shaping roll passes, constituting a progressive series; Figs.10 and 11 are elevations of finishing passes that perfect the circularshape of the formed tube and, particularly, fix the arcuate contour ofthe seam area in permanent form; Fig. 12 is a vertical section through apass to show the yieldable mounting of a roll housing to permit a passto adjust itself to variations in the position of the surfaces of ametal blank duringits passage; and Fig. 13 is a horizontal section of ayieldably mounted roll, as section AA of Fig. 12.

Referring more particularly to the drawings, in

which representative elements are numbered, it is evident that each passcomprises cooperating rolls mounted with shaping faces opposed to eachother, as rolls 1 and 2 of Fig. 2 and rolls 3, 4 and -5, 6 of Fig. 6,for example. Each pass contains one or more forming rolls to provide aconcave shaping face having its middle portion eliminated from thegeneral contour of the pass so that a. metal blank B that conformsgenerally to the pass bridges over the middle of the forming face. Forexample, in Fig. 2 there is a forming roll 2 with its middle portion cutaway peripherally, and in Fig. 6 there are two lateral forming rolls 3,4 spaced from each othersymmetrically so that the middle of the pass isfree from contact with the blank. With this arrangement, the rolls holda blank under pressure at the sides, but they afford no central pivotshould the pressures on the margins of the moving blank become unequal,as they do when the sheet varies in thickness or contains irregularitiesof surface. Either margin that may be held under increased prmsure tendsto be retarded in its passage, while the opposite edge under the lesspressure tends to advance relatively faster. Where the middle of a blankis subjected to pressure in a pass the strip thus tends to pivotsomewhat about the middle of the pass and to stretch the metal of themore rapidly advancing edge. The unequal lengthening effect iscumulative and in the aggregate tends to twist the seam considerablyfrom a straight line. But by eliminating the middle of the forming faceof a plurality of passes, the edges of a blank are caused to travel morenearly at equal rates despite any relative differences of pressure onthe margins of the blank, and thus the seam is kept in better alignment.There may be supporting faces for the middle of the strip, but theyapply no shaping pressure that would tend to pivot the moving blank.

In order that the shaping rolls may adapt,

themselves to surface irregularities of a blank, one or more of therolls of each pass is mounted yieldably so that the edges of the passadjust themselves to counteract inequalities of pressure. This isindicated in Figs. 2 and 8, with suitable structure illustrated more indetail in Figs. 12 and 13.

In Fig. 12 opposed shaping rolls 1 and 2 are mounted in a frame 33. Thelower roll 2 is shown journalled in a stationary housing, but the upperroll 1 is journalled in a housing 7, the upper side of which is seatedpivotally against avertically adjustable central pin 8 carried by theframe. The lower sides of the housing are supported on springs 9 and 10that serve to press the housing upwardly against the pivot pin 8. withsuch arrangement any relative increase of one side of the blank Bresults in lifting that side of the yieldable shaping roll 1, and thusequalizing the pressures at the edges of the pass.

Fig. 13, a cross section of the upper part of housing 7, along the lineAAof Fig. 12, shows a slight spacing of housing 7 from frame 33 along anarrow but long area of contact to permit the required pivotal play.Along their sides, however, housing '1 and frame 33 fit closely in orderto prevent any misalignment of the roll, toward the front or back.

In passes having exterior shaping rolls mounted vertically at oppositesides of the pass, as rolls 11 and 12 of Fig. 8, at least one of therolls is journalled in a vertically disposed arm, as 13, that ispivotally mounted to permit equalization of pressure at the edges of thepass.

Further elements of this invention appear in the mounting ofconvexrollers within the blank at the later passes of the series. Suchrollers afford lateral pressure outwardly in cooperation with theexternal rolls for completing the cylindrical shape of the blank. Sinceit has been difficult because of lack of space to mount rolls inside theblank where the seam edges converge and since a supporting arm ofappreciable length is disadvantageous, pairs of mutually-contactinginner rolls 1;! and 15 are mounted on bifurcated spindles 16 that extendthrough the narrow space of the closing-seam, as illustrated by Figs. '7and 8 or by rolls 5, 6 of Fig. 6. These rollers are not driven butrotate by their contact with the moving blank. As shown, the contour oftheir faces is appropriate to their position in the series of passes.They afford the outward thrust necessary to bend the considerable massof metal in heavy-wall material to the shape of the pass, and with anyblank they provide areas of maximum pressure that are balanced atopposite sides of the blank to prevent one edge creeping ahead of theother.

These inner rollers are guided by light spindles, but with their facesin contact with each other the burden on the spindles is negligible asthey transmit side thrust between their corresponding exterior rolls.The considerable pressures necessary for bending the side walls of heavytubes, must be counteracted, however, or

they would crush and destroy the normal contour of the convex faces ofthe inner rolls and thus lead to unequal movement of the walls of vtheblank and to aggravation of skewing of the seam edges. To prevent thiscrushing of the convex roller faces, the faces are flattenedperipherally at the middle. This avoids point contact, the flattenedcontact faces thus distributing and decreasing the unit pressure oftheir mutual contact. In this way the period of usefulness of theseinner rolls is increased, and they are better able to maintain properalignment of the side walls of a blank.

, Fig. 9 illustrates outer rolls and the mounting of inner rollers nearthe end of the series of passes, where the problem becomes morediflicult to bring the seam area to proper alignment. Here isillustrated a pass in which two external rolls 17 and 18 applyingpressure near the seam, cooperate with a vertically disposed pair ofinner rolls 19 and 20. Since the seam is substantially closed, the innerrolls mounting on a vertical spindle becomes impossible, and they areset loosely within the tube, contacting with each other and with thewalls of the tube, and held in place by plates 21 and 22 at their side.These plates extend in the tube as an arm, but they extend only arelatively short distance and sustain practically no load. Suchresultant thrust as is downward from outer rolls 1'7 and 18 may now beborne by the tubing itself or by a simple supporting roller under it.

Following the series of shaping rolls proper, is what may be termed asettingpass, shown in Fig. 10. The pass of Fig. 10 consists of threerolls 23, 24, 25. Roll 23 supports the'tubing and rolls 24 and 25 aremounted separately to apply pressure against opposite sides of the seamfor permanently setting the metal close to the seam to the contour towhich it has been brought by the shaping passes. This arrangement isuseful oecause of the considerable pressure necessary to overcome theexisting leverage of the metal at the edges and to bring the extremeedge area along the seam from flat to circular form. Where has beenunsatisfactory in practical operations to design roll bearings and facesadequate for the purpose, but a pass of three cooperating rolls toterminate the shaping passes permits a satisfactory practicalarrangement to accomplish the final setting of the edges in a dependablemanner.

Following this finishing pass for setting the edges is a final shapeadjusting pass of three rolls 26, 2'7, 28, Fig. 11, for perfecting thecircular contour of the walls of the tube.. In this pass two rolls aremounted for supporting the tube having arcuate faces that contactextensively. with the tube walls opposite the'seam. The third rolllikewise is arcuate and is mounted across the seam. With this mountingit is possible to arrange heavy. bearings so that these rolls betweenthem can apply considerable pressure over substantially the entire wallof the tube and adjust irregularities in its contour.

According to the provisions of the patent statutes, I have explained theprinciple and mode of operation of my invention and have illustrated anddescribed what I now considerto represent its best embodiment. However,I desire to have it understood that, within the scope of the appendedclaims, the invention may bepracticed otherwise than as specificallyillustrated and described.

I claim: 1. A tube-forming pass having generally parallel arcuateshaping faces with the middle of the pass faces removed from contactwith a blank lying in the general contour of the pass, said passcomprising opposed concave shaping rolls mounted symmetrically at thesides of the pass, and generally convex backing rolls opposed to saidconcave rolls and cooperating therewith to shape the edge portions of ablank. 2. A tube-forming pass having generally parallel, opposed shapingfaces with the middle portion of the pass removed from contact with atube blank lying in the general pass contour, and comprising lateralshaping faces at opposite sides of the pass mounted rockably relativelyto each other for adaptation to irregularities of surface alignment in ablank moving through the pass. 3. A tube-forming mill comprising aseries of shaping passes adapted to bend a strip of metal progressivelyto cylindrical form and containing concave rolls having shaping faces atopposite sides of a pass to leave the middle portion of the pass freefrom contact with a tube blank lying in its general contour, and innershaping rollers parallel to the lateral roll faces, the concave rolls atthe sides of the pass being mounted rockably relatively to each otherfor adaptation to irregularities of surface alignment in a moving blank.4. In a tube-forming mill, a shaping pass comprising a frame, a shapingface mounted in fixed position in said frame, a housing rockably mountedin said frame, a shaping roll journalled in said housing for cooperationwith said shaping face, a pivot bearing mounted in fixed position abovesaid housing, and springs acting between the sides of said housing andframe resiliently urging the housing into contact with said bearing,whereby variations in thickness transversely of tube blanks supplied tothe mill cause said housing and roll to rock about said fixed pivot inthe plane of the longitudinal axis of the roll and thereby to equalizethe pressure applied by the pass.

5. In a tube-forming mill, a shaping pass comprising a frame, a concaveroll journalled in fixed position in said frame, a housing rockablymounted in said frame, a convex shaping roll journalled in said housingfor cooperation with said concave roll, a pivot bearing mounted in fixedunyielding position in said frame above said housing, and springs actingbetween the sides of said housing and said frame resiliently urging thehousing into contact with said bearing, whereby variations in thicknesstransversely of tube blanks supplied to the mill cause said housing andconvex roll to rock about said fixed pivot in the plane of thelongitudinal axis of the roll and thereby to equalize the pressureapplied by the pass.

6. In a tube-forming mill, a shaping pass comprising a frame, opposedcooperating shaping rolls, one of said rolls being journalled in saidframe in fixed position, and the other of said rolls being journalledfor rocking in the plane of its longitudinal axis about a fixedunyielding pivot positioned centrally of the roll whereby the roll rocksin response to variations in thickness transversely of blanks suppliedto the mill and thereby equalizes roll pressure transversely of theblank.

7. A tube-forming pass comprising rolls mounted to form lateral shapingfaces at opposite exterior sides of the pass and rockable with respectto each other for adaptation to differences of surface alignment in atube moving through the pass, a pairof inner rollers forming interiorshaping faces supported within the blank to contact with each other andwith the interior of the blank opposite said exterior rolls tocounteract side thrust thereof, and spindles mounted within the blankcarrying said inner rollers.

REIMAR C. F. KURTZE.

